Medicinal cannabis should be more than pot luck

Should Australia move toward legalising marijuana? In the first of two pieces, Wayne Hall takes a look at the medicinal side of the cannabis question.

Governments face major policy challenges in meeting patient demands for ready access to safe, effective and affordable cannabis-based medicines.

There is reasonable evidence from controlled trials that drugs derived from the cannabis plant have some medical uses. Dronabinol and nabilone (which produce the effects of cannabis sought by recreational users) are better than a placebo in reducing nausea and vomiting in cancer patients. They also stimulate appetite in patients with AIDS-related wasting.

One problem is that this evidence comes from old, poorly done studies. There are now more effective treatments for nausea and vomiting in cancer, and we no longer have to treat AIDS-related wasting.

Patients now want to use cannabis to treat other disorders such as chronic pain and anxiety, depression and sleep problems. Here the evidence is thinner.

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Nabiximols, a standardised cannabis plant extract, reduces muscle spasticity and pain better than a placebo in patients with multiple sclerosis. These medicines reduce pain over periods of weeks, but they are only marginally more effective than a placebo: 21 per cent of patients who received cannabinoid drugs reported a 50 per cent reduction in pain – but so did 17 per cent who received a placebo. Twenty patients needed to receive the drug for one to benefit.

Cannabis can also help people to get to sleep, but the risks and benefits of its longer-term use for sleep (and chronic pain) are unclear. Doctors are understandably concerned about long-term risks, given the unhappy experiences with opioids for chronic pain and other drugs used to treat sleep problems.

Patients with pain, anxiety and sleep problems have demanded that the government allow them to use medical cannabis. Australian governments have responded by allowing patients to use the ‘special access provisions’ of the Therapeutic Goods Act to use unapproved cannabis-based medicines.

These special access provisions are typically used by patients with terminal illnesses who have failed to respond to conventional treatments. Governments have also licensed Australian companies to produce cannabis-based medicines. In the interim, patients can import cannabis products from overseas for medical use with a doctor’s prescription.

Patients have experienced three problems with this system. The first has been in finding doctors who are prepared to prescribe cannabis-based medicines. Doctors argue that there is an absence of evidence on the safety and efficacy of many proposed medical uses of cannabis. They also fear being sued for any harms suffered by patients.

The second problem has been navigating the different requirements of federal and state governments in order to import and use cannabis. These issues are now being addressed.

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The third problem is harder to solve: the cost of pharmaceutical-quality cannabis products. Backyard illicit cannabis medicines may be cheap to produce, but their quality is uncertain and variable. It costs money to produce consistent, medical-standard cannabis medicines that are free of contaminants and contain known doses of the active therapeutic ingredients.

These difficulties have prompted some silly policy proposals.

A One Nation Queensland MP introduced a private members bill into the Queensland Parliament that proposed allowing amnesty to patients and others to grow and use cannabis for medical reasons. It would also have required the government to cover the costs of obtaining them if patients were unable to pay for them.

The current enthusiasm for using medical cannabis contrasts sharply with the scepticism often shown towards the claims of pharmaceutical companies. The claims made by promoters of medical cannabis – some of whom have a financial interest in its use – are often uncritically accepted by the media and politicians in the absence of evidence of safety and efficacy, other than patient testimonials.

We should worry about the precedents we create by treating medical cannabis as a special case, exempt from usual requirements of evidence. We should avoid replicating the US experience in the 1970s with Laetrile, a supposed cure for cancer, that led many US states to pass laws giving patients the right to use the drug (although without the government paying for it).

We should also be wary of liberal medical cannabis laws being used to facilitate the legalisation of recreational cannabis use. This has arguably happened in the US, where states with medical cannabis laws that allowed any doctor to “recommend” cannabis for any illness paved the way for the legalisation of recreational cannabis use in those states.

There is a case to be made for legalising cannabis, but this should be made openly and publicly deliberated – not introduced by stealth in the guise of treating illness.